Reptilia · Squamata
Lachesis mutaLinnaeus, 1766
South American Bushmaster
Photograph by Leonel Roget, CC BY, via iNaturalist
A ground-dwelling, nocturnal, meat-eating snake from the Neotropic region, reaching 360 cm nose to tail.
Reptilia › Squamata › Viperidae › Lachesis
- Grows to
- 3600mm
- greatest recorded
- Eats
- Carnivorous
- Active
- Nocturnal
- Lives up to
- 31.6years
Longer than 99% of all vipers anyone has measured.
The bar is the rank itself: its length is the share of the family this animal exceeds. The chart below is the family’s real spread, on a logarithmic scale because body length here runs from 280 to 3,900 mm. The solid rule is this animal. Every bar is a count of real species, and nothing on this figure is estimated.
What is known
39 sourced facts, each taken from a named scientific dataset. How to read these.
Cited from a dataset unless a row is marked otherwise.
Standing in the world
- Still living
- Extant
- Conservation status
- Least Concern
- Status assessed · the year the Red List last looked
- 2015
The animal itself
- Limbs
- None
- Venomous
- Yes
- Fangs
- At the front of the mouth
- Longest recorded life
- 31.6years
Stark et al. 2020
Size
- Length nose to tail · greatest recorded
- 3600mm11 ft 10 in
- Body mass · greatestcomputed
- 21,669g48 lb
- Body mass · a typical adult
- 5817g13 lb
- Body mass · adult female, meanmeasured
- 375g13.2 oz
- Body mass at hatching
- 82.2g2.9 oz
snakes only in this source
computed from length by a family-level allometric equation, not weighed
AnAge rates this record "acceptable"
How it lives
- Diet
- Carnivorous
- How it hunts
- Sit and wait
- Active
- Nocturnal
- Where it lives
- Terrestrial
- Habitat
- Forest
- Biome
- Tropical & Subtropical Moist Broadleaf Forests
- Region
- Neotropic
- Mainland or island
- Mainland
- Highest it lives · above sea level
- 900m
- Range size
- 7,483,721km²
carnivore (see Pinto‐Coelho et al. 2021)
Sit (Glaudas et al. 2019)
da Frota et al. 2021, n = 1
Pinto‐Coelho et al. 2021, da Frota et al. 2021
0-900 (Señaris & Rojas-Runjaic 2020)
Breeding
- Reproduction
- Oviparous
- Sex decided by
- Genes, ZW/ZZ
- Gestation or incubation
- 77days
- Average clutch
- 8.5eggs
- Eggs or young per clutch
- 7–20eggs
- Mean clutch
- 8.5eggs
- Clutches in a year
- 1per year
- Clutches a year
- 1per year
- First breeds at
- 48months
- Age at first breeding · female
- 1460days
Feldman et al. 2015
mean 8.5 (Meiri et al. 2019), 7-20 (O'Shea 2011)
Naming and history
- Suborder
- Serpentes
- Infraorder
- Alethinophidia
- Subspecies
- No
- Described by
- Linnaeus
- Moved to another genus · since it was first described
- Yes
- Described in
- 1766
- Type locality
- Brazil
Keeping one
11 ft 10 in × 5 ft 11 in × 8 ft 10 in(360 × 180 × 270 cm)
Minimum length × width × height, for one animal. Bigger is always better.
The standard sizes snakes as a fraction of total length: 1 × 0.5 × 0.75.
Mindestanforderungen an die Haltung von Reptilien (Sachverständigengutachten), German Federal Ministry for Nutrition, Agriculture and Forestry, Animal Welfare Division, 10 January 1997. The standard states these floor areas are recommendations rather than binding limits.
From this animal’s own total length of 11 ft 10 in (3600 mm), at 1 × 0.5 × 0.75 times it, following the German federal welfare standard — how this is worked out.
No preferred body temperature has been recorded for South American Bushmaster. Rather than repeat a number from a care sheet, this page leaves it out.
Feeding
A prey item should be between the same width as the widest part of the snake's body and about 1.5 times that width.
Widely used across snake husbandry references. An alternative formulation gives prey at 10-15% of the snake's body mass. This is established practice, not a measurement.
1402kJ per day
Worked out for an animal of 21,669 g, the heaviest recorded for South American Bushmaster — so it is the top of the range, not a figure for a particular animal. Weigh yours and the number will be lower.
An upper estimate, not a feeding target, and not veterinary advice. The equation covers only what an animal burns staying alive, so a growing, gravid or recovering animal needs more — and it was measured on wild animals, which move far more than one in an enclosure. Body condition and a vet who knows the species are what a feeding decision should rest on. Where this comes from.
What nobody knows
These are not gaps in our research. No scientific dataset records them for this species — and saying so is information you cannot get from a reference that simply leaves a field out.
- — Length snout to vent · greatest recorded
- — Length snout to vent · adult female mean
- — Length snout to vent · adult male mean
- — Length snout to vent · adult mean
- — Female length · mean, nose to tail
- — Length nose to tail · adult male mean
- — Length nose to tail · adult mean
- — Largest female · snout to vent
- — Largest male · snout to vent
- — Largest female · shell length
- — Largest male · shell length
- — Hatchling length · snout to vent
- — Hatchling length · nose to tail
- — Largest juvenile · snout to vent
- — Largest juvenile · shell length
- — Egg length
- — Egg width
- — Preferred body temperature · chosen in a laboratory gradient
- — Body temperature when active · measured in the wild
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How the young develop
- — Hatchling length · smallest recorded
- — Hatchling length · largest recorded
- — Mature from · youngest recorded
- — Mature by · oldest recorded
- — Size at maturity · smallest recorded
- — Size at maturity · largest recorded
- — Body temp in the wild · lowest mean recorded
- — Body temp in the wild · highest mean recorded
- — Colour on the back
- — Pattern on the back
- — Pupil
- — Population trend
- — Red List criteria
- — Active season · shortest recorded
- — Active season · longest recorded
- — Density · lowest recorded
- — Density · highest recorded
- — Home range · largest recorded
- — Active in
- — Lowest it lives · above sea level
Others in Viperidae
Take this data
Everything on this page is available as data under CC BY 4.0 — use it freely, credit it, no permission needed.
This species as JSON · the whole dataset
Cite this page
The Reptile & Amphibian Encyclopedia (2026). Lachesis muta. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/lachesis-muta
@misc{lachesis_muta_2026,
title = {Lachesis muta},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/lachesis-muta}
}Sources
- Meiri, S. (2024). SquamBase — a database of squamate (Reptilia: Squamata) traits. Global Ecology and Biogeography. Public domain (CC0).
- AnAge, Human Ageing Genomic Resources (de Magalhães et al.), used under CC BY 3.0.
- Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
- Catalogue of Life (dataset 3LR), used under CC BY.